Summary Gastrointestinal cancers such as esophageal, gastric, and colorectal cancers represent some of the most challenging and lethal cancer types. Colorectal cancer alone is the third most common cause of cancer in men and women in the United States, despite implementation of colonoscopy for early detection. Esophageal and gastric cancers are less common, but their prognosis is dire if not detected early. The current standard of clinical practice uses conventional white light endoscopy, which is limited in that it offers only morphological information, has difficulties detecting microscopic lesions, and is highly operator dependent. Much greater benefits of upper and lower endoscopy would be anticipated if it would rely on specific molecular signals. To this end, we have developed a new generation of ultra-sensitive Raman nanoparticle beacons ? 4th generation SERRS-Nanostars (4G Nanostars) ? that after intravenous injection home specifically to both precancerous and cancerous lesions. They emit a unique Raman spectroscopic signature (?Raman fingerprint?) that clearly identifies the intestinal lesion. Because of the very high sensitivity (limit of detection in the attomolar range), even microscopic lesions of 100 m in size can be detected. The 4G- Nanostars were developed with a special eye towards clinical translation, and consist of inert materials. Importantly, a clinical Raman endoscope that can detect the 4G-Nanostars has already been developed. We will first characterize the 4G-Nanostars with the assistance of the NIH Nanotechnology Characterization Laboratory to ensure optimal formulation and exclude any unexpected adverse effects ahead of in vivo studies. We will then determine optimal dosage in mice, and use non-invasive dynamic positron emission tomography imaging to quantify the biodistribution of 4G-Nanostars in organs and intestinal lesions. 4G-Nanostar uptake into esophageal, gastric and colonic lesions will be quantified and ranked according to the histological classification of each lesion, in order to determine if they can be used to noninvasively discriminate different lesion types. Subsequently, we will determine the accuracy with which 4G-Nanostars can detect the intestinal lesions in both mouse and large animal models of esophageal, gastric and colon cancer. We will test the accuracy of 4G-Nanostar imaging using a clinical Raman endoscope developed by our collaborators. We will also evaluate the use of SERRS-Nanostars as a theranostic agent using photothermal ablation. In summary, this proposal aims to establish a fundamentally new and highly translatable method that will allow more sensitive and specific detection and ablation of both (pre-)malignant lesions of the esophagus, stomach, colon and rectum. The experiments are designed thoroughly and rigorously so that at the end of the grant period all data has been acquired to file an IND for a clinical trial.